This application is based on Application No. 2000-279106 filed in Japan, the contents of which is hereby incorporated by reference.
The present invention relates to an image display apparatus, and in particular, to an image display apparatus such as a projector and an HMD (head mounted display) in which a two-dimensional image rendered on an illuminated LCD (liquid crystal display) is projected and displayed onto a screen or viewer""s eyes.
In an ordinary image display apparatus for displaying a two-dimensional image rendered on a reflective LCD, the LCD display plane is illuminated by illuminating light composed of specific polarized light (for example, p-polarized light), whereby specific polarized light (for example, s-polarized light) in the reflected light is extracted as image light. The image light is then introduced onto a screen or a viewers s eye by a magnifier optical system, whereby the two-dimensional image is magnified and projected. Japanese Laid-Open Patent Publication No. 11-125791 proposes an image display apparatus for magnifying and projecting a two-dimensional image by using a magnifier optical system arranged in a decentered manner with respect to the display plane of a reflective LCD. The magnifier optical system is composed of an eccentric prism for correcting the deformation (trapezoidal distortion and the like) caused by the decentered optical configuration. However, the eccentric prism needs complicated design and fabrication processes, thereby causing an increase in the cost of the apparatus.
This complication in the magnifier optical system is avoided by arranging the magnifier optical system concentrically with respect to the display plane of the reflective LCD. However, this causes the necessity of optical path separation between the illuminating light onto the LCD and the reflected light from the LCD. In a first prior art example shown in FIG. 9, the optical path separation between the illuminating light and the reflected light is carried out by a reflective polarizer film (4A). An image display apparatus having such configuration is proposed in U.S. Pat. No. 5,900,976 and the like. Illuminating light emitted from an LED (light emitting diode; 1) is diffused when passing through a diffuser plate (2), and then passes through a condenser lens (3). After that, p-polarized light alone passes through the reflective polarizer film (4A), thereby illuminating a display plane (5a) of an LCD (5). The LCD (5) controls the polarization of light selectively depending on the display at each pixel of a two-dimensional image (that is, the ON/OFF state of each pixel), thereby emitting the reflected light composed of two kinds of polarization (p-polarized light and s-polarized light). In the reflected light, s-polarized light alone is reflected by the reflective polarizer film (4A), thereby serving as image image light. The light is then introduced onto a screen or a viewer s eye by a magnifier optical system (6; AX indicates optical axis).
In a second prior art example shown in FIG. 10, the optical path separation between illuminating light and reflected light is carried out by a prism-type PBS (4B; polarizing beam splitter). Illuminating light emitted from an LED (1) is diffused when passing through a diffuser plate (2), and then passes through a condenser lens (3). After that, p-polarized light alone passes through the PBS (4B), thereby illuminating a display plane (5a) of an LCD (5). The LCD (5) controls the polarization of light selectively depending on the display at each pixel of a two-dimensional image (that is, the ON/OFF state of each pixel), thereby emitting the reflected light composed of two kinds of polarization (p-polarized light and s-polarized light). In the reflected light, s-polarized light alone is reflected by the PBS (4B), thereby serving as image light. The light is then introduced onto a screen or a viewer""s eye by a magnifier optical system (6; AX indicates optical axis).
In the first prior art example, an air region is present in the optical path between the LCD (5) and the magnifier optical system (6). Accordingly, for the purpose that a sufficient back focal length of the magnifier optical system (6) is prepared for arranging the illumination system comprising the condenser lens (3) and the like, the focal length of the magnifier optical system (6) needs to be longer. This causes a difficulty in obtaining a wider angle of view or a wider angle of field. On the other hand, in the second prior art example, the larger and heavier PBS (4B) composed of two prisms prevents size and weight reduction of the apparatus. An object of the present invention is to provide an image display apparatus for permitting the viewing of an image, wherein a magnifier optical system is substantially in concentricity with a display plane, wherein illuminating light from a light source passes through a first plane and then through a second plane, thereby illuminating the display plane, and wherein reflected light from the display plane passes through the second plane and is then reflected by the first plane, thereby passing through a third plane and then being incident on the magnifier optical system.